Lubricating fluids facilitate the reduction of friction (i.e. lubricate), remove heat (i.e. cool), flush away impurities, preserve or improve surface quality, and protect, e.g., tools and machine parts from damage, wear and corrosion as far as possible. In addition to the functions described above, ideal lubricating fluids have the following desirable functions and properties: inhibit corrosion, low foam formation, low toxicity, microbial resistant, waste treatment friendly, biodegradable, and non-objectionable odor.
For example, lubricating fluids are frequently used in metal working processes, e.g., cutting, grinding, forming, lapping, drawing, forming, pressing, punching, rolling, stamping, etc. Metalworking fluids are often straight oil (vegetable or animal oil or fat, a mineral oil, synthetic oil or a mixture thereof) or water-based fluids. Water-based metalworking fluids include soluble oils, which contain less than 2% by weight of water; semi-synthetic fluids, which contain 10-60% by weight of water; synthetic fluids, which are petroleum oil-free and can contain any water-soluble lubricity additive; and neo-synthetic fluids, which use vegetable oil and/or animal oil instead of petroleum and may contain an emulsifier, corrosion inhibitors, alkanolamine, and water. Metalworking fluids may also include agents, for example, an oiliness improver, an extreme pressure agent, a corrosion inhibitor (e.g. a rust preventative), a surfactant, a preservative, an antioxidant, etc.
Petroleum oil rich metalworking fluids are utilized in nearly 80% of metalworking operations. Petroleum based metalworking fluids, however, have several drawbacks, for example: (1) poor heat conductivity and therefore, limited ability to cool; (2) misting results in petroleum residues that are difficult to remove; (3) the emulsion stability is often effected by water hardness; and (4) not environmentally friendly and therefore, result in disposal difficulties.
Amine-containing metalworking fluids are being employed because the amines (e.g. alkanolamines) increase bio-resistance, corrosion protection, and emulsion stability. Effective water-based metalworking fluids are difficult to formulate without employing amines. However, amines can be very toxic. Furthermore, synthetic petroleum oil-free (i.e. water-based) metalworking fluids currently on the market have limited lubricity and stability. As such, there is a need for metalworking fluids that are effective lubricants, which are stable for an extended period of time, and contain less hazardous compounds (e.g. reduced amine content).
DIACID 1550 is often employed in lubricating fluids because it is a co-emulsifier that inhibits corrosion (extends machinery life), has lower bioactivity (prolongs fluid life), and has increased hard water tolerance compared to mixed and fatty acids. As such, employing DIACID 1550 results fewer additives in the lubricating fluid because it functions to lubricate, prevent corrosion, co-emulsifies, etc. However, DIACID 1550 is limited in its hard water tolerance (i.e. stability in hard water), and produces foam when utilized in metalworking fluids.
Therefore, there exists a need to for lubricating fluids that have increased stability (i.e., longer shelf-life), performance in hard water, suitable lubricity, and reduced foam formation during use, e.g., metalworking.